The use of implantable fluid medication dispensers is well known. These devices typically include a medication reservoir within a generally cylindrically shaped housing. Some form of fluid flow control is also provided to control or regulate the flow of fluid medication from the reservoir to the outlet of the device for delivery of the medication to the desired location, usually through a catheter. The flow control may be provided by a pumping or metering device such as disclosed in U.S. Pat. No. 4,692,147 issued to Duggan. Other forms of flow control are disclosed in U.S. Pat. Nos. 3,951,147 and 4,360,019.
All implantable fluid medication dispensers must also include some means to replenish the fluid medication in the medication reservoir. The previously mentioned U.S. Pat. Nos. 4,692,147 to Duggan and 3,951,147 to Tucker et al. disclose typical reservoir refill assemblies. Both include an opening or port through which a resealable septum may be accessed. To refill the reservoir a hypodermic needle is inserted through the septum and into a chamber between the septum and a needle stop, which may be a plug or filter. The medication is injected under pressure into the chamber and flows into the Reservoir.
A disadvantage of these reservoir refill assemblies is that they have been stacked on top of the reservoirs. Thus, the external housing of the device must be sized not only to accommodate the depth of the reservoir but, additionally, the depth of the refill assembly including the septum, the chamber and the needle stop. This adds considerably to the total depth of the drug dispensing device which is undesirable, especially in view of technological advances being made in the miniaturization of other components of the device. Since the device is implanted in the body it is advantageous to make the device as small as possible. A smaller (thinner) device can be implanted in smaller people and in children and allows all patients to be more active.